June 2003 Shark Bytes
Posted on Monday, 30 June 2003
Greetings Shark Lovers!
The longer I am involved in sharks and nature, the more I am convinced that one can never count on knowing anything for sure about these animals. In the eight years that we have been observing white sharks at Seal Island we have always recorded phenomenally high numbers of white shark predatory events on Cape Fur Seals.
This past month, which in past years has been the peak month, we have seen a 47% decrease in activity.
We have seen 23 successful predations (P) and 29 attempted predations (AP). To give you all an idea of this decline, last year in June we recorded 110 actual events. The sharks’ success rate is still very high at 44%, but it does not seem as though many sharks are predating on seals.
When we are anchoring up and get the sharks up to the boat we are not seeing constant numbers of sharks either. One day we will see 12, then the next day we will see 5 and very seldom are we seeing the same sharks from day to day.
There are a few theories that we have come up with, the most important being weather. We still have not had one cold front come through, bringing with it the ideal conditions for predatory behavior. In fact we are experiencing pre-shark season weather! This means that there are still summer fish in the bay and we have actually had yellow-tail (amberjack) feeding in our chum slick! As I mentioned last month the sharks would far rather feed on the fish than the seals. I must mention that 90% of the sharks we have seen do seem to have been feeding, so the yellow-tail could be a possible source.
Another interesting point is that the Sardine-Run along the Natal South Coast has not happened as yet, making it more than a month late. So maybe we will have a late season?
Indeed a very worrying factor is that since last season Seal Island has had an increase in human impact with more operators inter-acting with the sharks. We already saw a decrease in predatory behavior last year and really hope that this is not responsible for the downward trend.
Sport fishermen have also been involved in hooking white sharks and we saw 2 sharks with large hooks and trace protruding from their mouths. Unfortunately they are clearly targeted hooks and it is devastating for us that this illegal activity is still rife. The authorities know about this, but nothing is being done to stop it. The only positive factor is that we are at Seal Island everyday during peak season and we will prevent this happening.
We feel that very interesting times await Seal Island…
One of the most rewarding aspects of being at Seal Island is that over the years we have gotten to recognize and learn the personalities of many different white sharks and each year we anxiously await their return.
The first such shark to return was “Notch Fin”. He is a regular who was first recorded in 1997 and seems to stay around Seal Island the whole season. We saw him on 7 occasions in June as well as at 2 kills. It is very difficult to identify sharks at predations as it all happens very quickly. Notch Fin has a very distinct notch out of the top of his Dorsal fin, making his identification much easier. I guess we weren’t too creative in naming him!
We were extremely excited to see him in such good condition and we estimate him to be at around 3.9 meters in length with a sizable girth!
Another favorite shark back at Seal Island is “Night Rider”. He is one of the most aggressive and confidant sharks we see and can make life rather difficult for us when he is around the boat going for baits. We have noticed that he has grown significantly from 3.6 meters last year to 3.8 meters this year so he must have had a very successful past year to achieve this.
Last year we did not see “Lighthouse” and when she returned this year we nearly did not recognize her. She was 4 meters when we last saw her in 2002 and she is now 4.3 meters, a very big shark! In the past she was always very relaxed around the boat and when we saw her in June she was just the same. We recognize her by a white circle at the top of her upper caudal lobe. It was very encouraging for other sharks we have not seen that even though we did not see her last year she did return two years later.
We also managed to identify a shark that was tagged in May 1999. This was a 1490 day resight for us. This female shark had grown 70 cm in the 4 year period.
These constant resightings leads us to believe that most of the sharks do return each winter where they feed on Cape Fur seals.
Over the last few weeks we have gotten to know another shark well as he has been at the boat most days.